Project description
Study sheds more light on the unusual properties of large aromatic rings
Molecules such as benzene are known as aromatic compounds. If a magnetic field is directed perpendicular to the plane of an aromatic system, a ring current is induced in the delocalised pi electrons of the aromatic ring. Aromaticity was long thought to be restricted to small molecules, but recent research has shown that circuits of more than 160 pi electrons can exhibit strong aromatic ring currents. The EU-funded ARO-MAT project will explore the effects of molecular size and topology on aromaticity. The study will focus on the electronic and magnetic phenomena in molecules with dimensions of 5–25 nm (as big as many proteins). Fundamental knowledge generated during the project could serve as a basis for developing materials with unprecedented electronic and magnetic properties.
Objective
ARO-MAT will target emergent cooperative electronic and magnetic phenomena in molecules with dimensions of 525 nm (i.e. as big as many proteins). The project will develop supramolecular architectures with large pi-systems and well-defined geometries, in which the frontier orbitals coherently delocalize charge over the whole nanostructure. Aromaticity is a key emergent phenomenon; it can be defined as the ability of a cyclic molecule to sustain a ring current when placed in a magnetic field. Until recently, it was thought that aromaticity is restricted to small molecules, with circuits of less than about 22 pi-electrons. Anderson has shown that circuits of more than 160 pi-electrons (circumference > 15 nm) can exhibit strong aromatic ring currents. Testing even larger rings will elucidate the link between aromaticity and the persistent currents found in non-molecular mesoscopic rings (diameter 50500 nm). ARO-MAT will explore the effects of molecular size and topology on nanoscale aromaticity. Other emergent phenomena to be addressed include the formation of open-shell singlet polyradical ground states, magnetic bistability in systems with many paramagnetic metal centers, and the control of charge transport through single-molecule devices by quantum interference. This multidisciplinary project combines organic synthesis, supramolecular chemistry, theory, electronic structure calculations, NMR and EPR spectroscopy, magnetochemistry, molecular electronics and low-temperature charge transport experiments. The core objective is to create low band gap materials with unprecedented electronic and magnetic properties, and to understand the structure-property relationships governing the behavior of these new materials. Most of the target structures are based on metalloporphyrins because of their redox activity, stability, structural versatility, suitability for template-directed synthesis and ability to position multiple strongly coupled paramagnetic metal centers.
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Funding Scheme
ERC-ADG - Advanced GrantHost institution
OX1 2JD Oxford
United Kingdom